ABSTRACTWith the exploitation of rare earth ore, more and more REEs came into groundwater. This was a waste of resources and could be harmful to the organisms. This study aimed to find an efficient adsorption material to mitigate the above issue. Through doping sodium alginate (SA) with poly-γ-glutamate (PGA), an immobilized gel particle material was produced. The composite exhibited excellent capacity for adsorbing rare earth elements (REEs). The amount of La3+ adsorbed on the SA-PGA gel particles reached approximately 163.93 mg/g compared to the 81.97 mg/g adsorbed on SA alone. The factors that potentially affected the adsorption efficiency of the SA-PGA composite, including the initial concentration of REEs, the adsorbent dosage, and the pH of the solution, were investigated. 15 types of REEs in single and mixed aqueous solutions were used to explore the selective adsorption of REEs on gel particles. Scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectroscopy analyses of the SA and SA-PGA gel beads suggested that the carboxyl groups in the composite might play a key role in the adsorption process and the morphology of SA-PGA changed from the compact structure of SA to a porous structure after doping PGA. The kinetics and thermodynamics of the adsorption of REEs were well fit with the pseudo-second-order equation and the Langmuir adsorption isotherm model, respectively. It appears that SA-PGA is useful for recycling REEs from wastewater.

Mentions:
Distinct differences were observed in the morphologies between SA and SA-PGA gel beads (Fig 4). Fig 4A and 4E show the shapes of wet gel particles. Compared with the SA, SA-PGA had a larger size because of doping with poly-γ-glutamate(average diameter 1mm). The color of SA gel appeared semitransparent, but the SA-PGA particles were milk white. After freeze drying, the color of SA-PGA gel darkened. Fig 4C, 4D, 4H and 4I present SEM images (Hitachi S3400N SEM, Japan). Under 2000x magnification, SA-PGA exhibited a uniform porous structure, whereas the structure of SA appeared compact and non-porous. Consequently, SA-PGA had a larger specific surface area, which was beneficial to improve the adsorption efficiency.

Mentions:
Distinct differences were observed in the morphologies between SA and SA-PGA gel beads (Fig 4). Fig 4A and 4E show the shapes of wet gel particles. Compared with the SA, SA-PGA had a larger size because of doping with poly-γ-glutamate(average diameter 1mm). The color of SA gel appeared semitransparent, but the SA-PGA particles were milk white. After freeze drying, the color of SA-PGA gel darkened. Fig 4C, 4D, 4H and 4I present SEM images (Hitachi S3400N SEM, Japan). Under 2000x magnification, SA-PGA exhibited a uniform porous structure, whereas the structure of SA appeared compact and non-porous. Consequently, SA-PGA had a larger specific surface area, which was beneficial to improve the adsorption efficiency.

ABSTRACTWith the exploitation of rare earth ore, more and more REEs came into groundwater. This was a waste of resources and could be harmful to the organisms. This study aimed to find an efficient adsorption material to mitigate the above issue. Through doping sodium alginate (SA) with poly-γ-glutamate (PGA), an immobilized gel particle material was produced. The composite exhibited excellent capacity for adsorbing rare earth elements (REEs). The amount of La3+ adsorbed on the SA-PGA gel particles reached approximately 163.93 mg/g compared to the 81.97 mg/g adsorbed on SA alone. The factors that potentially affected the adsorption efficiency of the SA-PGA composite, including the initial concentration of REEs, the adsorbent dosage, and the pH of the solution, were investigated. 15 types of REEs in single and mixed aqueous solutions were used to explore the selective adsorption of REEs on gel particles. Scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectroscopy analyses of the SA and SA-PGA gel beads suggested that the carboxyl groups in the composite might play a key role in the adsorption process and the morphology of SA-PGA changed from the compact structure of SA to a porous structure after doping PGA. The kinetics and thermodynamics of the adsorption of REEs were well fit with the pseudo-second-order equation and the Langmuir adsorption isotherm model, respectively. It appears that SA-PGA is useful for recycling REEs from wastewater.